Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $127.26   11.528%   $141.9305   $141.93   $141.95   $141.90  
  Purchase #2 $137.68   8.228%   $149.0083   $149.01   $149.00   $149.00  
  Purchase #3 $57.53   10.728%   $63.7018   $63.70   $63.70   $63.70  
  Purchase #4 $244.87   7.380%   $262.9414   $262.94   $262.95   $262.90  
  Purchase #5 $71.26   6.123%   $75.6232   $75.62   $75.60   $75.60  
  Purchase #6 $112.88   8.277%   $122.2231   $122.22   $122.20   $122.20  
  Purchase #7 $250.72   5.414%   $264.294   $264.29   $264.30   $264.30  
  7 purchase totals = $1,002.20       $1,079.7223   $1,079.71   $1,079.70   $1,079.60